1. Field of the Invention
The present invention relates to a fluid compressor for compressing refrigerant gas in a refrigerating cycle, for example.
2. Description of the Related Art
There have been well known compressors of various types such as those of the reciprocating and rotary types. In these compressors, however, the compression section and driving parts, such as the crank-shaft for transmitting a rotary force to the compression section, are complicated in construction so that consequently a large number of components must be used. Further, in these conventional compressors, it is required that a check valve be arranged on the discharge side thereof to enhance compression efficiency. However, the pressure difference on both sides of the check valve is quite large, thereby causing a gas leakage through the check valve. This lowers the compression efficiency appreciably. In order to solve this problem, it is required that the dimensions and assembly of parts used be highly accurate. As the result, the cost for manufacturing the compressor is very high.
U.S. Pat. No. 2,402,189 discloses a screw pump having a columnar rotating body provided with suction-and discharge-side ends. The rotating body is arranged in a sleeve, and a spiral groove is formed on the outer circumference of the rotating body. A spiral blade is slidably fitted into the groove. When the rotating body is rotated, fluid, which is introduced into a space between the outer circumference of the rotating body and the inner circumference of the sleeve and is confined between two adjacent turns of the blade, is transferred from one end of the sleeve to the other end. In short, the screw pump serves only to transfer the fluid from one end of the sleeve to the other end, and is not adapted to compress it.
In the above-mentioned screw pump, the volume of fluid transferred is proportional to the pitches of the spiral groove and blade. When the pitches of the groove and blade are large, therefore, the volume of fluid than can be transferred by the pump is large. In this case, however, the dimensions of the rotating body, sleeve and the like become larger as the pitches of the groove and blade increase. As a result, the whole pump becomes large and burdensome.